<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../../../JQuery/JQuery/jquery-3.5.1.min.js"></script>
</head>
<script>
    window.onload = function(){
        document.getElementById("btn1").onclick = function(){
            alert(1);
        }
        $("#btn2").click(function(){
            alert(2);
        });
        $("#btn2").bind("click", function(){
            alert(3);
        });
    }
</script>
<body>
    <button id="btn1">btn1</button>
    <button id="btn2">btn2</button>
</body>
</html>